Personal computers usually have at least a disk drive to serve data storage means. The disk drive used in a personal computer can be classified as floppy disk drive which use a floppy magnetic disks, such as 51/4" disks or 31/2 disks, and hard disk drive (also referred to as fixed disk drive).
For floppy disks, a write protection notch is provided on the enclosure thereof. Once the notch is covered by, for example, a section of an adhesive tape, the disk drive is prohibited to write data to the protected disks. There is, however, no similar device for protecting hard disks from being written accidently or undesirably.
Currently, there is commercial software available in the market for protecting the hard disks from being accidently over-written. The disadvantage is that to execute such software, the main memory space of the computer must be occupied by the software and thus reducing the availability of the main memory space. Further, the central processing unit of the computer is also shared by such a software when the software is executed and thus lowering the efficiency of the central processing unit in handling other jobs.
It is therefore desirable to have a hard disk write protection device in the form of hardware so as to prevent undesired write action of the hard disks while maintaining the original availability of the main memory space and the central processing unit to the users of a computer.